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Bureau of Mines Information Circular/1981 






Preventing Large-Battery Explosions 



By D. Cummins and S. F. Pangerl 



UNITED STATES DEPARTMENT OF THE INTERIOR 



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Information Circular 8842 



Preventing Large-Battery Explosions 



By D. Cummins and S. F. Pangerl 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 




/ 



This publication has been cataloged as follows: 



Cummins, David 

Preventing large-battery explosions. 

(Information circular - Bureau of Mines ; 8842) 

Bibliography: p. 11. 

Supt. of Docs, no.: I 28.23:8842. 

I. Electricity in mining— Safety measures. 2. Storage batteries- 
Safety measures. 3- Mine explosions. I. Pangerl, S. F., joint author. 
II. Title. III. Series: United States. Bureau of Mines. Information cir* 
cular ; 8842. 

T N ' 205.U4 - [TN343] 622s [622 '.8] 80-606996 



"It 

CONTENTS 

v^ Page 
'O 

^ Abstract 1 

^ Introduction 1 

^ Acknowledgments 1 

The lead-acid battery 2 

Background 2 

Recent developments 2 

Battery care and maintenance 3 

Jumping batteries 4 

Field service examples < . 7 

Discussion 7 

Safety considerations 7 

Sources of sparks or flames 8 

Conclusions and recommendations 9 

Bibliography 11 

ILLUSTRATIONS 

1. Offset slave cable connector 5 

2. Off center slave cable connector 5 



'On 






PREVENTING LARGE-BATTERY EXPLOSIONS 

by 

D. Cummins ^ and S. F. Pangerl^ 



ABSTRACT 

This Information Circular presents a brief history of the lead-acid bat- 
tery and describes ways to prevent serious injury from battery explosions when 
servicing and charging lead-acid batteries, particularly in the surface raining 
industry. The Mining Safety and Health Administration (MSHA), U.S. Consumer 
Product Safety Commission, battery manufacturers, and the mining industry have 
all contributed information as well as recommendations for injury-free han- 
dling for this report. 

INTRODUCTION 

Mining industry employees are exposed to an increasing number of acciden- 
tal explosions when hooking up lead-acid batteries (especially the larger 
sizes used on big equipment) for routine charging in the shop or temporary 
boosting in the field. These battery explosions, created by igniting ever- 
present hydrogen, often inflict acid burns to eyes and other parts of the 
body. An analysis of current MSHA and U.S. Consumer Product Safety Commission 
accident statistics indicates that workers are either not fully aware of the 
hazards associated with lead-acid batteries or become complacent. 

This information circular is not intended to be a technical handbook. 
Instead it seeks to acquaint the reader with a variety of situations that can 
cause battery explosions and ways to prevent them. Data are summarized from 
handbooks, textbooks, and manufacturers' technical data sheets, together with 
the authors' personal observations in operating mines. 

ACKNOWLEDGMENTS 

MSHA and the Department of Consumer Protection helpfully provided statis- 
tics and advice on the basic study. The following representatives of private 
industry provided technical assistance: Jerry E. Berger, Support Manager, 

^Chemical engineer. 
^Engineering technician. 

Both authors are with the Spokane Research Center, Bureau of Mines, Spokane, 
Wash. 



Health, Safety and Environment, Shell Oil Company, Houston, Texas; Ken 
Marshall, Vice President and General Manager, KW Battery Co., Skokie, 111.; 
and J. L. Rooney and Chris Morris, Vice Presidents (Operations), Chloride 
Industrial Batteries, Kansas City, Kan. 

The following mining sites were visited to discuss field experience: 
Washington Irrigation and Development Co. (WIDCO), Centralia, Wash.; Butte 
Operations, Berkely Pit, Anaconda Operations, Anaconda, Mont., Big Horn Mine, 
Sheridan, Wyo. ; Morrison-Knudsen Co., Inc., Sarpy Creek Industrial Mining, 
Hardin, Mont.; and Decker Mine No. 1, Decker, Mont. 

THE LEAD-ACID BATTERY 

Background (_5)^ 

The lead-acid storage battery has been used for over 100 years. During 
the 1920 's, the battery replaced the magneto, carbide headlamps, and the hand- 
crank starter on cars and trucks. In recent years, several improvements have 
increased battery life and battery-charge capacity. Most improvements are 
confined to better methods of plate forming and reduction of impurities in the 
electrodes. 

Today's batteries give optimum performance for several services. Sta- 
tionary batteries generally use weaker acid for longer life. Portable batter- 
ies use stronger acid for larger charge capacity. Impurities in the sulfuric 
acid and in the battery plates significantly affect battery performance. Gas- 
sing (hydrogen production) can be caused by even traces of several impurities. 

Hydrogen gas produced in the lead-acid battery is the primary source of 
battery explosions. Local action produces a small, continuous supply of 
hydrogen; however, the largest amount is generated during charging. This 
hydrogen production increases as the battery approaches full charge. Gradu- 
ally reducing the charging current will minimize this tendency. As the lead 
ions plate out, excess current carries hydrogen ions instead of lead ions to 
the negative electrode. 

Recent Developments 

The maintenance-free battery uses a lead-calcium alloy instead of lead- 
antimony. The alloy aids in reducing hydrogen generation. Some maintenance- 
free batteries are sealed and do not need water during their normal life. One 
battery manufacturer states its maintenance-free battery produces less than 5 
percent of the hydrogen produced by the standard lead-antimony battery. 

Another new product is the spark-arresting ceramic vent, made with fine 
pores that prevent flames produced outside the battery from getting inside and 
causing an explosion. In a clean atmosphere, plugging of the vent is no prob- 
lem. However, in a dusty atmosphere around most surface mines, plugging of 

^Underlined numbers in parentheses refer to items in the bibliography at the 
end of this report. 



these vents can cause pressure to build inside the battery and rupture the 
case. Thus, frequent cleaning may be required in the field. 

"The Hydro-Catalator Corporation has developed a catalyst battery cap 
which converts hydrogen and oxygen to water. The caps have a dual function of 
preventing the escape of hydrogen from the cells and restraining the loss of 
water from the cells" O). 

These caps have not been tested in surface mining equipment. One battery 
source suggested these caps may not function properly in vehicles traveling 
over rough terrain where battery acid could be splashed onto the active 
element. 

BATTERY CARE AND MAINTENANCE 

Many battery problems are caused by improper care and maintenance, 
although most battery companies provide information on proper care. Good 
maintenance includes frequent cleaning to remove either metal dust or coal 
dust and any corrosion present. Metal dust can drain current from the bat- 
tery. Coal dust having a high sulfur content is also corrosive. Under 
extreme dust conditions, the battery vent can plug, causing the case to rup- 
ture. Corrosive buildup between the cable clamp and terminal post increases 
electrical resistance, reducing the amount of deliverable power, and can drain 
current away from the battery. Several products are on the market for protec- 
ting battery terminals against corrosion. Corrosion on the battery clamps and 
terminal posts can be removed with a water solution of either washing powder 
or baking soda. Fizzing of the soda solution indicates the presence of acid. 
When all the acid has been neutralized, the fizzing will stop. 

Tamping the cable clamps onto the posts with a hammer can do major 
damage. Also, using a screwdriver to pry the clamp off the post can separate 
the post from the lid. If the battery post is broken inside the battery, a 
resulting spark can cause an explosion. Special clamp pullers are available 
for removing cable clamps without damaging the bond between post and lid. 
When installing a fresh battery, always spread the clamps open before sliding 
them over the post. Then tighten the clamp for a good connection. This pre- 
vents rapid corrosion between post and clamp or the chance of spark during 
engine start. 

If the battery is not firmly held in the battery box, bouncing from off- 
road service can damage the plates or the case. Actual location of the bat- 
tery in the vehicle is important for several reasons. Workers have suffered 
back strain when removing batteries because of an awkward lifting angle. Acid 
may splash if the battery strap breaks or becomes loose during removal. Loca- 
tion also plays a major role in the ventilation of hydrogen gas that may accu- 
mulate in the storage box. 

The liquid in the battery should be checked frequently and maintained at 
the proper level. A low liquid level provides space for a large accumulation 
of gas, which increases the intensity of an explosion. A low liquid level 
also may expose the plates, with the chance for sparks and a resulting 



explosion. A high liquid level increases the chance of battery acid seeping 
out. 

Never touch the two battery terminals with a pair of pliers or other 
metal objects to judge the charge by the size of the spark; if hydrogen is 
present in sufficient quantity, an explosion can result. It is also important 
to have the right polarity when connecting a dead battery to a charger. A 
battery charged with polarity reversed will have its life shortened and can be 
a hazard. 

Jumping Batteries 

Battery explosions on mining equipment can be reduced by using a safe 
procedure for jumping weak batteries; for example, a battery should never be 
jumped when the liquid is frozen. The rapid heating produced by jumping will 
cause expansion, possibly rupturing the case. The battery should be brought 
into a warm building and allowed to thaw slowly. Five conditions or acts can 
trigger explosions when batteries are jumped. 

1. Sparking at the battery terminal when the last jumping cable is con- 
nected, or when the first cable is removed after engine start. 

2. Connecting jumping cables with the wrong polarity. Wrong polarity 
may destroy the diode in the alternator and can explode the battery. 

3. Connecting batteries of different voltages (that is, 12-volt to 
24-volt). 

4. Jumping a frozen battery. 

5. A broken terminal post causing sparks inside the battery. 

Three kinds of jumping cables may be used: slave cables, standard 
cables, and extra-long cables with a switch in the middle of one cable. 

With the slave-cable setup, a plug-in connector is hard-wired to the side 
of the vehicle 2 to 4 feet from the battery. Some slave cables are held in 
one bundle and fixed to connect with only one polarity — positive (+) to posi- 
tive (+), and negative (-) to negative (-). Two methods of achieving this are 
illustrated in figures 1 and 2. In figure 1, the terminals are offset about 
one-half inch. In figure 2, the terminals are mounted off center in a plug-in 
socket. 

Standard jumping cables consist of two heavy-duty wires with alligator 
clips on both ends. 

The third kind of cable is an extra-long standard cable with a switch in 
the middle of the black, or negative line. 



Slave coble 

receptacle base 

Mounted on vehicle 



* M. ' . i M. ' .M '' M. i 



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|i;p^|5imjmBJ 



Slave coble 
Terminal 





FIGURE 1. - Offset slave cable connector. 




Section-/4-/4 



The fourth kind is 
called a "combination" 
cable. It is a jumping 
cable with a slave-cable 
connector put on one end and 
alligator clips on the other 
end. 

With the slave cable 
setup, there is no risk of 
sparks near the battery, and 
the plug-in connector will 
only go together with the 
correct polarity. The lid 
on the battery box should be 
closed when the slave cables 
are being connected and when 
the engine is cranked. If 
the battery explodes, no 
acid will be splashed on the 
mechanic. This is a safe 
procedure. 

With standard jumping 
cables, a strict jumping 
procedure must be followed. 
The generally recommended 
check procedure follows 
(1, 5): 



Slave cable 
receptable bose 

Mounted on 
vehicle 




Slave coble 
terminol 



FIGURE 2. - Offcenter slave cable connector. 



1. Batteries must have 
same voltage. 

2. Both negative posts 
grounded. 

3. Check fluid level; 
check for freezing. 

4. Vehicles not 
touching. 



5. Ignition accessories off. 

Only then ATTACH alligator clips in following order, and REMOVE in 
reverse order: 



1. Attach one red clip to positive terminal on weak battery. 

2. Attach the other red clip to positive terminal on good battery. 



3. Attach black clip to negative terminal on good battery. 

4. Attach other black clip to vehicle FRAME, a foot or more from weak 
battery. 

In the surface mining industry, it is common to use both negative-ground 
and positive-ground equipment. Here, extra care should be taken to connect 
the batteries correctly. There are TWO critical rules to follow. ALWAYS con- 
nect like terminals — positive (+) to positive (+), and negative (-) to nega- 
tive (-). ALWAYS make the last connection on the FRAME of the vehicle with 
the weak battery. ALSO, remove the cable connected to the FRAME first when 
disconnecting the jumper cables. Sparks will occur when completing an elec- 
trical circuit, and sparks will occur when breaking an electrical circuit. To 
avoid an explosion, keep all sparks a foot or more from the battery. 

Additional safety may be achieved by placing a damp cloth or towel over 
the battery before attaching cables. A damp cloth can reduce the chance of a 
flame getting inside the battery to produce an explosion, and can prevent acid 
being splashed if an explosion does occur. In freezing weather, a dry cloth 
can be used. 

When using extra-long cables with an in-line switch, the alligator clips 
should be attached — negative to negative — with the switch off. Next, connect 
positive to positive. The person can stand back about 8 feet, and turn on the 
switch to avoid splashing acid, should an explosion occur. 

In case one battery has a slave-cable terminal and the other does not, 
use a "combination" jumping cable. The two alligator clips should be attached 
first. Then, the slave-cable connector should be plugged in. "Combination" 
cables are as safe as regular slave cables. However, it is necessary to 
attach the alligator clips with the correct polarity. 

Slave cables provide a safe way to jump batteries. In most mines, slave- 
cable attachments are not installed on all vehicles, so an additional set of 
cables may have to be carried on the service vehicle. 

The extra-long jumping cable with an in-line switch may be the least 
expensive, safest, and most versatile jumping cable. When the switch is 
turned off, this cable can be attached to both batteries in any sequence, and 
the only care that must be observed is connecting like polarities — positive to 
positive, and negative to negative. No problem develops when the two vehicles 
have opposite ground polarities — just connect positive to positive, and nega- 
tive to negative. If the service truck has a 24-volt system consisting of two 
12-volt batteries, a weak 12-volt battery can be jumped by attaching the alli- 
gator clips to one of the good 12-volt batteries. 

When using standard jumping cables, there is less built-in safety, and 
extra caution is required, compared with that using slave cables or cables 
with an in-line switch. 



If both vehicles have negative grounds, one list of safe jumping steps 
can be used. However, if both negative-ground and positive-ground vehicles 
are in use, then there are four possible combinations of safe jumping steps. 

Field Service Examples 

At one mine, a specially equipped truck services all disabled vehicles. 
Two heavy-duty, 12-volt batteries in the back of the truck are hard-wired to 
extra-long jumping cables with an in-line switch. Switches in the battery box 
permit these batteries to be charged from the truck's alternator, then discon- 
nected. The jumping cables can be switched to one battery for 12 volts or to 
both batteries for 24 volts. With this switch setup, any vehicle can be 
serviced. 

In another mine, a battery box with two heavy-duty, 12-volt batteries is 
mounted on a small trailer pulled by the service truck. A slave-cable connec- 
tor is attached to the outside of the battery box. Three sets of jumping 
cables are used to fit any situation: slave cables, standard jumping cables, 
and a "combination" cable. 

In cold weather, it was found that connecting to the weak battery and 
charging for 5 minutes improves starting. Current flowing through both bat- 
teries warms them and increases their available power. 

DISCUSSION 

Safety Considerations 

1. All lead-acid batteries contain hydrogen gas above the liquid. 

2. Hydrogen, in small amounts, is continuously generated in lead-acid 
batteries. 

3. The primary production of hydrogen occurs during the charging cycle, 
especially as the battery approaches full charge. 

4. To prevent excess hydrogen production, limit the charging current. A 
voltage regulator will reduce the charging current as the battery approaches 
full charge. 

5. Maintenance-free batteries produce much less hydrogen than standard 
lead-antimony batteries. 

6. Well-ventilated battery installations reduce the amount of explosive 
atmosphere in the battery vicinity. 

7. When the only practical location for the battery is in the cab under 
the seat hydrogen gas is more likely to accumulate because of the poor venti- 
lation. The maintenance-free battery would be of special interest here or in 
any location with poor ventilation. 



8. A weak spark is sufficient to ignite hydrogen. The minimum energy 
to ignite hydrogen is about 10 percent of the energy needed to ignite methane 
(natural gas) (_2). 

9. Most battery explosions occur when a flame or spark is produced 
within a few inches of the battery. When the hydrogen gas ignites, the flame 
can feed back through the battery vent igniting the gas inside. Because the 
volume of gas is relatively small, the explosion is relatively small. The 
major hazard is from splashing battery acid, especially in the face and eyes. 

10. In contrast to small inner-battery explosions where acid splash is 
the chief hazard, there is the possibility of an explosive blast in a confined 
area outside the battery, as illustrated in this unusual accident: hydrogen 
filled the vehicle cab, and the explosion knocked the mechanic down and blew 
the cab door several feet away. The battery under the seat was being charged, 
and the operator forgot to turn off the charger. The 8- to 10-hour overcharge 
created enough hydrogen to form the combustible mixture. 

11. In addition to explosions, injury can occur from lifting heavy bat- 
teries. This is especially true with large equipment when the battery box is 
in an inconvenient location. This can be remedied by substituting three 
smaller 8-volt batteries for a 24-volt system. 

Sources of Sparks or Flames 

1. Attaching jumping cable to battery post or removing from the post. 

2. Arcing across the battery post from — 

a. Dropping a metal tool across post accidentally. 

b. Using a metal tool to short battery to judge the amount of 

charge by the length of spark produced. 

3. Using a match to check the liquid level in battery. 

4. Smoking and allowing cigaret to pass close to battery vent. 

5. Allowing cable clamp to remain loose around battery post. 

6. Sparking caused by making or breaking an electrical circuit (shut 
off all accessories). 

7. Static electricity developed from wearing synthetic fabric clothing 
in dry weather. 

8. Sparks occur inside a battery: 

a. When a heavy current is drawn through a broken terminal post. 

b. When a short occurs between two plates with low liquid level. 



CONCLUSIONS AND RECOMMENDATIONS 

Most physical battery handling occurs in the battery shop. Here 
batteries are cleaned, tested, repaired, and charged — and accidents are mini- 
mal. Safety reports indicate most battery explosions occur when vehicles are 
serviced in the field and not by battery personnel in the shop. If everyone 
were as safety conscious about hydrogen escaping from batteries as they are 
about fumes escaping from gasoline fuel systems, most battery explosions would 
be prevented. All personnel handling batteries should have safety training, 
such as safety meetings and training films. 

Battery accidents are more hazardous in the field than in the battery 
shop where gloves, aprons, and safety glasses are generally worn and safety 
showers are available for removing acid. In the field, there are no facili- 
ties for quickly washing off acid splash nor is there protection from rubbing 
eyes with acid on the hands. 

Three types of cables (slave, "combination," and in-line with switch) 
place a person out of reach of danger when completing the final connection. 
To achieve comparable safety with a standarad jumping cable, cover the battery 
or wear protective clothing. Covering the battery with a damp cloth or towel 
is much simpler. In freezing weather, use a dry cloth. 

Even when a list of safe jumping steps is followed, mistakes occasionally 
are made. Also, an explosion can occur if there is a broken post inside the 
battery. Never have your unprotected face over an uncovered battery when 
starting the engine. 

The best recommendation is to use experienced personnel familiar with 
battery operation and service. However, when personnel with minimum experi- 
ence are called upon to service batteries, certain safety steps must be 
followed. Slave cables, "combination" cables, or cables with an in-line 
switch will reduce chance of injury. But if standard jumping cables are used, 
all vehicles should have procedure decals at battery location or equally visi- 
ble place stating: 

1. Batteries must have same voltage. 

2. Both negative posts grounded. 

3. Check fluid level; check for freezing. 

4. Vehicles not touching. 

5. Ignition off, accessories off. 

Only then ATTACH alligator clips in following order, and REMOVE in 
reverse order. 

1. Attach one red clip to positive terminal on weak battery. 



10 



2, Attach other red clip to positive terminal on good battery. 

3, Attach one black clip to negative terminal on good battery. 

4, Attach other black clip to vehicle FRAME, a foot or more from weak 
battery. 

When two vehicles have the same voltage, but different polarities, there 
are TWO must considerations: ALWAYS make the last connection, which produces 
the spark, on the frame away from the battery; and ALWAYS remove this connec- 
tion to the frame first. ALWAYS connect terminals of like polarity — positive 
to positive, and negative to negative. 

For added safety, place a damp cloth or towel over an uncovered battery 
before attaching cables. In freezing weather, a dry cloth can be used. Stand 
back before starting engine. 

Make sure all accessories are turned off when installing a new battery or 
removing an old battery. 

As an added precaution, the following safety tips should be observed: 

1. Don't smoke or use matches around the battery. 

2. Don't wear spark-producing synthetic fabrics near the battery. 

3. Keep battery terminals washed free of corrosion. 

4. Apply approved materials for corrosion protection to battery 

terminals. 

5. Keep battery tied down snug in the battery box. 



11 



BIBLIOGRAPHY 

1. Berger, J. The Unexpected Dangers Book. Shell Answer Book No. 12, Shell 

Oil Co., Houston, Tex., 1978, p. 5. 

2. Litchfield, E. L. Minimum Ignition-Energy Concept and Its Application to 

Safety Engineering. BuMines RI 5671, 1960, 10 pp. 

3. Morley, L. A., and J. A. Kiefer. Coal Mine Electrical System Evaluation. 

V. Battery and Battery-Charging Safety. BuMines Open File Rept. 61(5)- 
78, Feb. 15, 1977, p. 32, grant GO 155003; available for reference at 
Bureau of Mines facilities in Denver, Colo., Twin Cities, Minn., Bruce- 
ton and Pittsburgh, Pa., and Spokane, Wash.; U.S. Dept. of Energy facil- 
ities in Carbondale, 111., and Morgantown, W. Va.; National Mine Health 
and Safety Academy, Berkley, W. Va. ; and National library of Natural 
Resources, U.S. Dept. of the Interior, Washington, D.C. 

4. U.S. Department of Transportation. Battery Hazards. Consumer Services 

Fact Sheet, Nat. Highway Traffic Safety Admin., July 1975, 4 pp. 

5. Vinal, G. W. Storage Batteries. John Wiley & Sons, Inc., New York, 

4th ed., 1955, 446 pp. 



T^U.S. GOVERNMENT PRINTING OFFICE: 1981-703-002/14 int.-bu.of min es,pgh.,p a. 25216 



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